Signal problems at 5th Ave-59th St. in Manhattan and Queens Plaza wrecked commutes on six lines Tuesday, forcing trains to be rerouted, and delaying service.

Four signals went dark during the outage, forcing trains to move slowly through the tracks, backing up service.

NYC Transit chief Andy Byford, who was hoping to provide some good news at a board meeting Tuesday on subway improvements, said he's investigating the signal outages, which disrupted service from 5:30 a.m. about 12:30 p.m.

"It meant that we just couldn't move the numbers of people that we needed to," Byford said. "It did give commuters a horrendous experience."

There was repair work done in the area over the weekend, Byford said, though it's unclear if it's related to the signal meltdown in Queens and Midtown.

Still, Byford said the $800 million Subway Action Plan that MTA Chairman Joe Lhota launched last summer is working and the proof is in the stats. Byford pointed to the drop in "major incidents" that hold up at least 50 trains.

December saw 50 of these major disruptions, down from 76 incidents in the same month in the prior year.

There was repair work done in the area over the weekend, Byford said, though it's unclear if it's related to the signal meltdown in Queens and Midtown.

(D. Reed / New York Daily News)

NYC Transit tweeted out updates as the disruptions were happening.

“Some southbound R via F line from Roosevelt Av to 57 St-7 Av because of signal problems at Queens Plaza,” said one message.

“Some southbound R trains are running along the F line from Jackson Hts-Roosevelt Av to Lexington Av-63 St then via the Q line to 57 St-7 Av because of signal problems at Queens Plaza,” the agency added later.

“Yikes! With morning N train service disruptions, the line for the M60 bus from Astoria is wrapped around the block! ?? #MTA #Ntrain,” tweeted straphanger Julie Huntington, who snapped a picture of a huge queue for bus service around 6 a.m.

The MTA later sent an update on its repairs.

“Service Update: Our crews are on the scene working to fix it as quickly as possible. We will keep you updated,” it said.